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How to replace a hotend thermistor (MK3S/MK3S+)

How to replace a hotend thermistor (MK3S/MK3S+)

How to replace a hotend thermistor (MK3S/MK3S+)
Relevant for:
Last updated 3 months ago
How to replace a hotend thermistor (MK3S/MK3S+)
 Difficulty
Moderate
 Steps
15
 Available languages
CSDEESFRITJAPL

Step 1 Introduction

Introduction
Introduction
Introduction
This guide will take you through the replacement of the thermistor in the extruder on the Original Prusa i3 MK3S and MK3S+.
Some parts might slightly differ. However, it does not affect the procedure.
If the thermistor is damaged, you will see the MINTEMP error message on the display.
All necessary parts are available in our eshop shop.prusa3d.com
Note that you have to be logged in to have access to the spare parts section.

Step 2 Tools necessary for this guide

Tools necessary for this guide
Tools necessary for this guide
Tools necessary for this guide
Tools necessary for this guide
To replace hotend thermistor, please prepare:
1.5 mm Allen key
2.0 mm Allen key
2.5 mm Allen key
Needle-nose pliers
Cloth or piece of fabric 15x15cm

Step 3 Preparing the printer

Preparing the printer
Preparing the printer
Turn the printer off and unplug it!
Before you proceed, it is recommended to protect the heatbed.
Take off the flexible steel sheet.
Use any cloth or piece of fabric, which is thick enough and cover the heatbed. This will ensure you won't damage (scratch) the surface during the disassembly.

Step 4 Disconnecting of the thermistor

Disconnecting of the thermistor
Disconnecting of the thermistor
Disconnecting of the thermistor
Disconnecting of the thermistor
Using an Allen key release the M3x40 screw and open the door.
Cut the two zip ties on the cable bundle. Avoid cutting the cables!
Release two screws on the cable clip and remove the clip.
Disconnect the thermistor cable from the EINSY board.

Step 5 Removing the textile sleeve

Removing the textile sleeve
Removing the textile sleeve
Removing the textile sleeve
Removing the textile sleeve
Pull out the textile sleeve from the cable bundle and remove it all the way to the extruder.
Cut the two lower zip ties on the cable holder. Avoid cutting the cables.
If you have a zip tie on the heating cable and the thermistor cable, carefully cut it off.

Step 6 Extruder surgery

Extruder surgery
Extruder surgery
Extruder surgery
Extruder surgery
Release and remove the M3x20 (M3x18) screw from the hotend fan. Note that the fan-shroud might fall off.
Leave the other two screws holding the hotend fan in place. No need to remove them.
Release and remove both screws and remove the Front print fan.
Carefully insert the Front print fan in the X-axis belt.

Step 7 Removing the thermistor

Removing the thermistor
Removing the thermistor
Removing the thermistor
Loosen the grub screw at the bottom of the heaterblock with using the 1.5 mm Allen key.
WARNING: Do not pull the thermistor cable. Follow the instructions!
Using the Allen key gently push the thermistor out.

Step 9 Thermistor installation

Thermistor installation
Thermistor installation
Insert the thermistor to the heaterblock.
Secure by tightening the lock screw. Do not overtighten the set screw. It may damage the thermistor or the screw.
Ensure the thermistor is properly inserted and not move!

Step 11 Tightening the textile sleeve

Tightening the textile sleeve
Tightening the textile sleeve
Tightening the textile sleeve
Tightening the textile sleeve
Use two zip ties and push them through the upper slots on the cable-holder.
ATTENTION! Before tightening the zip ties add the cables from the hotend. Use the channel in the printed part to arrange them properly.
Once the hotend cables are included, tighten the zip ties and cut remaining parts.
Open the textile sleeve and insert the cables from the hotend.
Compare the look of the cable management with the last picture.
The zip tie arrangement was tested with the injection molded double spool holder (provided in the kit and assembled later on). If you intend to use any other frame mounted type holder, make sure the zip ties won't crash into it, which might result in a print failure.

Step 12 Guiding the textile sleeve

Guiding the textile sleeve
Guiding the textile sleeve
Guiding the textile sleeve
Guiding the textile sleeve
Before we proceed further, we need to twist the textile sleeve. This will prevent the cables inside to slip out during the printing.
Using your fingers gently twist the sleeve (not the cables) and create several wraps.
Twisting the sleeve will effectively shorten its length.
Slide the sleeve in the holder at least 3/4 of the holder's height.
Ensure the nylon filament isn't pushing the motor cables and if needed slightly unwrap the sleeve and push the filament up.
Use the Extruder-cable-clip and two M3x10 screws to fix the cable bundle in place.

Step 13 Cable guiding

Cable guiding
Cable guiding
Manage all cables in the Einsy base like in the picture. And secure it with two zip ties.
Secure the cable bundle with two zip ties.

Step 14 Final check

Final check
Final check
Final check
Final check
NOTE: Before these steps remove the protective cloth from the heatbed.
WARNING: Avoid touching the HOT nozzle!!!
Plug in the printer and turn it ON.
On the printer's screen navigate to the Preheat menu.
Select PLA.
Navigate back to the Info screen and check if the temperature rises.

Step 15 It's done!

It's done!
It's done!
Good job! You just replaced the thermistor on the extruder.
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